﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;

namespace TPA.DataAccess
{
    public static class PredicateBuilder
    {
      public static Expression<Func<T, bool>> True<T> ()  { return f => true;  }
      public static Expression<Func<T, bool>> False<T> () { return f => false; }
 
      public static Expression<Func<T, bool>> Or<T> (this Expression<Func<T, bool>> expr1,
                                                          Expression<Func<T, bool>> expr2)
      {
        var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
        return Expression.Lambda<Func<T, bool>>
              (Expression.OrElse (expr1.Body, invokedExpr), expr1.Parameters);
      }
 
      public static Expression<Func<T, bool>> And<T> (this Expression<Func<T, bool>> expr1,
                                                           Expression<Func<T, bool>> expr2)
      {
        var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
        return Expression.Lambda<Func<T, bool>>
              (Expression.AndAlso (expr1.Body, invokedExpr), expr1.Parameters);
      }
    }
}

 
